The Christmas carol 'Good King Wenceslas' is about the Duke of which region?

The Christmas carol 'Good King Wenceslas' tells a story about a Bohemian duke who braves the winter weather to give alms (money and food) to a poor peasant on the Feast of Stephen (26th December). The story is based on the life of Saint Wenceslaus I, Duke of Bohemia (AD 907–935).

Wenceslaus I was the duke of Bohemia in the modern-day Czech Republic from 921 until his death in 935. He was assassinated by his younger brother, Boleslaus the Cruel. His death increased his reputation for heroic virtue, resulting in his elevation to sainthood. Although Wenceslas was only a duke, legends about his life elevated him to the status of a king in the mind of the storytellers.

The lyrics to 'Good King Wenceslas' were written by the English hymnwriter John Mason Neale in 1853. It was first published in a series of poems and songs called 'Carols for Christmas-Tide' later that year. The carol was set to the melody 'Tempus adest floridum' ('Easter time has come'), a 13th-century melody.